The following is from The Spiritual in Art:
Abstract Painting, 1890-1985, copublished by the Los Angeles County Museum
of Art and Abbeville Press (1986) as an in-depth companion volume to the
exhibition shown in Los Angeles, Chicago and The Hague in 1986 and
1987:

Hilma af Klint was born in Sweden on 26 October 1862, into a family
that included several generations of naval officers skilled in navigation,
mathematics, and astronomy. She herself was interested in mathematics and
even more so in botany. In addition, she began at an early age to study
portrait painting. She neglected the study of languages and is said to
have understood only the Scandinavian ones, a factor that may have
intensified her subsequent isolation from the artistic movements of
Europe. As a child and during her student years she was susceptible to
extrasensory experiences and at seventeen became seriously involved in
spiritualism. At the same time af Klint continued to develop her abilities
as an artist and in 1882 entered the Royal Academy in Stockholm, where she
was esteemed by the faculty. After five years of study she was awarded a
studio of her own in which she worked professionally as a portrait and
landscape painter.

Together with four other women she formed a spiritualist group during
the 1890s. The Friday Group, or the Five, as they called themselves, began
as an ordinary spiritualist group that received messages through a
psychograph (an instrument for recording spirit writings) or a trance
medium. The members of the group -- af Klint, Anna Cassel, Cornelia
Cederberg, Sigrid Hedman, and Mathilde N. (family name unknown) -- met in
each other's homes and studios. Over the years af Klint became
mediumistically adept and eventually functioned as the sole medium of the
group. During the Friday Group's séances spirit leaders presented
themselves by name and promised to help the group's members in their
spiritual training; such leaders are common in spiritualist literature and
life.

Through its spirit leaders the group was inspired to draw automatically
in pencil, a technique that was not unusual at that time. When the hand
moved automatically, the conscious will did not direct the pattern that
developed on the paper; the women thus became artistic tools for their
spirit leaders. In a series of sketchbooks, religious scenes and religious
symbols were depicted in drawings made by the group collectively. The
group's drawing technique developed in such a way that abstract patterns,
dependent on the free movement of the hand, became visible....

Af Klint considered the knowledge of duality to be the main theme, or
message, of her work. She believed that the sexes of men and women in the
real world are reversed in the astral world; and that this reversal
provides a resolution of the duality within human existence. The struggle
between male and female is an expression of creation, and af Klint
believed that this struggle was the fundamental idea behind all creative
power. Formal elements and colors in her paintings can be related to this
duality. Her work leads the observer to the conclusion that when the
balance between male and female is attained one can leave the physical
plane and join the angels.